1. Field of the Invention
The present invention relates to a variable inductor element having a piezoelectric actuator and a mobile wireless apparatus.
2. Related Art
There are known techniques for driving a mirror or lens using a temperature, electrostatic force, electromechanical impulse, and magnetic force (see JP-A 2003-209981 (Kokai)).
A piezoelectric actuator having a piezoelectric element manufactured using MEMS (Micro Electro Mechanical System) technology has recently been attracting attention. A piezoelectric element manufactured by MEMS technology is characterized by its small size and large driving force. There have been proposed variable inductors using piezoelectric actuators of this type (see JP-A 2004-304154 (Kokai) and JP-A 2001-76935 (Kokai)). In a piezoelectric actuator disclosed in JP-A 2004-304154 (Kokai), a dielectric sheet on which a spiral inductor is formed is arranged on a substrate on which the other spiral inductor is formed. By moving the dielectric sheet on the substrate, the degree of overlap between the two spiral inductors is varied to change the inductance. The dielectric sheet is moved by electrostatic driving force generated from a linear actuator. Because the whole dielectric sheet is moved, a large amount of driving force is necessary. Therefore, there is a problem in which it is difficult to quickly move the dielectric sheet and power consumption is also large.
In a variable inductor disclosed in JP-A 2001-76935 (Kokai), two loop inductors whose magnetic fluxes overlap with each other are prepared, and the magnitude of magnetic coupling between the two inductors is variably controlled by changing the angle of one of the inductors. However, since the inductor, whose angle is varied, is arranged on a substrate, the angle cannot be set to below the surface of the substrate, and an angle range within which the inductor can move is limited. JP-A 2001-76935 (Kokai) also discloses several methods for varying an angle. Any of the methods cannot drive an inductor with a small driving force and suffers from problems of higher power consumption, a lower driving speed, and the like.